Olefin polymerization



Feb. 21, 1939. H L; GERHART ET AL I OLEFIN POLYMERIZATION 4 Sheets-Sheet l Filed June 19, 1936 KESQQ 7 INVENTORS Howard L, Gerharf Feb. 21, 1939.

H. L. GERHARTVEIT AL.

OLEFIN POLYMERIZATION 4 Sheets-Sheet 3 Filed June 19, 1936 ohomk X QEQ INVENTORS Howard]... Ger/7am H m N. B

Feb. 21, 1939;

H. L. GERHART ET AL 2,148,] 16

OLEFIN POLYMERI ZATION Filed June 19, 1936 4'Sheets-Sheet 4 MQN wQN

INVENTORS HoWardLGer/varf Ma BY hiFI/v son TORN Y I Patented F b. '21, 1939 uN1r1-:o STATES 2,148,116 mm POLYMEBIZATION Howard L. Gerhart, Philadelphia, Pa and Maurice H. Arveson, Chicago, Ill., assignors to Standard Oil Company; Chicago, 111., a corporation oi In Application June 19, 1936, Serial No. 86,077

15 Claims. (01. 196-1 0) This invention relates to the polymerization of a an admixture of olefln-containing hydrocarbons and, particularly, the normally gaseous oleflnic hydrocarbons containing the butylenes suchas 5 -n-butylene and isobutylene. Admixtures of gases containing the butylenes and propylene are par ticularly adapted for polymerization by our process and we may use an admixture of gases comprising mostly butylenes and propylene as the unsaturated constituents. Gases containing butane, the butylenes and propylene, are also adapted for polymerization by our invention. These gases may be derived from any suitable source such as the unsaturated gases produced by'the cracking of hydrocarbon oils for the manufacture of gasoline. Products from the debutanizer reflux drum of a cracking unit are particularly desirable.

The object of our invention is to provide improved systems for preventing loss of boron fluo ride, boron chloride or similar catalytic material which is used to effect the polymerization. A further object is to provide a method and means for increasing the yields of polymerization produc'ts falling within the gasoline boiling range in processes employing normally gaseous oleflnes such as butlyenes and propylene. A further object is to provide. improved means for preventing the lossof boron fluoride from the system and for recovering and recyclingboron fluoride in a closed system A further object is to provide an improved arnangement of' reaction chambers, ,heat exchangers, i'ractionating devices, scrubbers and catalyst recovery apparatus whereby maximum yields of desirable polymers may be obtalned at a minimum cost. A further object is to provide systems. for initially employing high polymerization temperatures followed by the formation of boron fluoride complexes at lower temper- 0 atures and subsequent recovery of boron fluoride by a. high temperature treatment. Other objects will be apparent as the detailed description of the invention proceeds.

, We have discovered that boron halides, such as boron trifluoride and boron trichloride polymerize a substantial quantity or the unsaturated hydrocarbons present in an admixture of hydrocarbon "cases with the attendantformation of an unknown type of reaction product between the boron halide, and the hydrocarbons undergoing polymerization and that this boron halide-hydrocarbon-complex will decompose at elevated temperatures into two products, namely,-boron halide and hydrocarbons. We prefer to use BF: and our invention" will be describedwith reference to .into the coils l2.

;for controlling reaction temperatures) this method, the feed gases entering the system The boron fluoride recovered from the boron fluoride-hydrocarbon-complex is reused in the process and the hydrocarbon is recovered along with the other polymers, a substantial portion of which boil within-the gasoline boiling range. 5

Our invention will be more clearly understood from the accompanying drawings which form a part of this disclosure and in which:

Figure 1 is a diagrammatic elevational plan or flow sheet of a preferred embodiment of our in- 10 vention.

Figure 2 is a flow diagram of another modification with parts shown in vertical section of a similar system employing an improved reaction tower. 15 Figure 3 is a flow diagram of a further modi flcation of the general type of system shown in Figure 1, but with the employment of a second low temperature polymerization step.

Figure 4 is still another flow diagram of a mod- 20 iflcation combining features of the process described in Figures 1 to 3.

Referring to Figure 1, gases containing oleflns, preferably an admixture of gases containing propylene and butylenes as the predominating 25 constituents, in either the gas or liquid state, enter the system through line, l0, are raised by compressor or pump H to the desired pressure, passed through the coils l2 in the temperature regulator I3 and then passed by line It to the 30 cooler l5. Steam, hot oil or any suitable heating or cooling medium may be circulated around the heating coils l2 in the temperature regulator I 3 by aid of conduits l6 and I! for the purpose of heating the feed gases in the coils to a tempera- 35 ture within the range of 300 to 700 F. The pressure maintained within the coils l2 may vary from 20 to 500 lbs. per square inch gage.

Gaseous boron fluoride enters the system through conduit I8, is raisedto the desired pres- 40 sure by the compressor l9 and passed by line 20 We prefer to introduce the catalyst intocoils l2 at a point intermediate the two ends of the temperature regulator (exchanger I3.'By 45 are heated up to a temperature between 300 and 700 F. before they are brought into contact with the boron fluoride. Usually about one-third o1 the coils are employed for the purpose of pre- 5 heating the gases as described but of course this may be varied. Under the conditions maintained in the coils'll, the boron fluoride polymerize's a.

substantial proportion of the unsaturated gases into normally liquid polymers, asubsta'ntial pro- 5 g portion of which boils within the gasoline boiling range, namely, below about 420-410 F. The boron fluoride hydrocarbon complex is unstable at temperatures above about 250, particularly at temperatures above 300 F. and by operating the temperature regulator II at temperatures above 300 F. this complex is not formed in coils l2; however, it is formed in other parts of our process as hereinafter described.

The cooler I reduces the temperature of the products passing therethrough to about 200 F. or lower so that the boron fluoride-hydrocarbon complex will be formed with some of those unsaturated hydrocarbons which escape polymeriza tion-in the coils i2. Any suitable cooling medium may be circulated through the cooler l5 with the, aid of conduits 2| and 22 for. the purpose of maintaining the desired temperature in the cooler. We have found it desirable to operate cooler l5 at temperatures within the range of 90 to 200 F.

The products pass from cooler l5 by conduit 23 to the lowerpart of the tower 24 which may be called a scrubber. The temperature in tower 24 is maintained below 200 F. and usually within the range of 90 to 200 F. and'in this tower the boron fluoride gas and unsaturated gases which escape polymerization in the previous part of our process are permitted to rise up through the tower where they are contacted with polymers in a manner to be described later and there react to form the boron fluoride-hydrocarbon complex. We prefer to maintain a temperature gradient in tower 24 ranging from 200 F. or lower in the bottom part of the tower to about 100 F. or lower in the top part of the-tower. A cooler 25 may be provided in the top part of the tower in order to maintain the desired temperature. A portion of the unreacted gases, particularly some of the saturated gases that-were present in the feed stock, may pass overhead from tower 24. Baffle plates or any suitable means 23 may be placed in the tower 24 in order to insure intimate contact between the boron fluoride gas and unsaturated hydrocarbons. At the temperature maintained in tower 24, none of the polymers or boron fluoride-hydrocarbon complex passes overhead.

The liquid products are withdrawn from the bottom of tower 24 through conduit 21 and passed to the separator 28 where the polymers and liquefled constituents are permitted to separate from the boron fluoride-hydrocarbon complex. The later compound being heavier than, and immiscible with, the liquid polymers, settles to-the bottom part of separator 28, the interface being shown by the line 29. A portion of the liquid hydrocarbons is withdrawn from the top part of the separator through line 30 with the aid of pump 3| and returned to the top part of tower 24 to be passed down through the tower and react with boron fluoride to form the boron fluoridehydrocarbon complex. If desired, a cooler may be placed in line 30 in order to assist in maintaining the desired temperature in the top part of tower 24. Other materials available in'the system may be used in tower 24 to contact boron fluoride to form the boron fluoride-hydrocarbon complex. For example, hydrocarbons from decomposed complex to be described later are picked up by pump Ila, are sent through line 30 into tower 24. Likewise, a heavy polymer fraction to be described later, may be used. The remainder of the free polymers and unreacted feed in the upper part of the separator 28 are withdrawn through line 32 and passed to the heat exchanger 33 and are then introduced into the fractionating tower 34.

The boron fluoride-hydrocarbon complex in the lower part of separator 28 is withdrawn through line 35 with the aid of pump 36 and passed by valved conduit 31 to the top part of the stripper 38 or passedby valved conduit 39 to an intermediate section of the coils l2 in the temperature regulator l3; If desired, a portion of the boron fluoride-hydrocarbon complex may be passed through valved conduit 31 and the other portion passed through valved conduit 39. At the temperatures maintained in temperature regulator II the complex is decomposed into boron fluoride and a free polymer. This boron fluoride then assists in the polymerization of the feed stock. We prefer to introduce theboron fluoride-hydrocarbon complex into coil I2 at about the same point where the initial charge of boron fluoride gas enters the coils.

The temperature in stripper 38 is maintained above 200 F. and preferably within the range or 250-350 F. so that the boron fluoride-hydrocarbon complex will be decomposed into boron fluoride gas and free polymer. are provided in the bottom part of tower 38 so as to maintain the desired temperature therein and fractionating means such as baille plates and trays 4! may be provided in tower 38 so as to assist in the efficient decomposition of the complex. The boron fluoride gas liberated from the complex is withdrawn from the top of the heater 38 through line 42 and returned to line 20 where it is again introduced into the coils I2. The liquid polymers in the lower part of the heater or stripper 38 are withdrawn through valved conduit 43 and passed to about the middle portion of the fractionating tower 34 or a portion or all may be sent through line 43a, pump 3ia, line 30 to tower 24 as previously described.

The fractionating tower 34 is of the conventional type and is operated in a manner well known to the art. The unreacted hydrocarbon gases, largely saturated hydrocarbon gases, which pass overheadfrom tower 24 through line 44, enter the fractionating tower above the middle portion thereof. The free polymers and balance of the unreacted fed recovered in the top part of the separator 28 are passed by line 32 to the fractionating tower, preferably entering the fractionating tower below the trap-out plate 45. Trapout plate 46 is provided in the lower part of the tower and the heavy polymers are withdrawn therefrom by conduit 41, passed to the reboiler 48 and then returned by line 49 to the bottom part of the tower. The reboiler provides sufficient heat Heating coils 40 to efiect'the desired fractionation in tower 34.

heat exchanger 33 and then are passed to storage through line 5| and a"portion of this stream may be sent through line 5Ia, line 43a, pump 3la, line 30 to tower 24 where it is used to react with boron fluoride to form the boron fluoride-hydrocarbon complex and/or provide cooling as previously described. The hydrocarbons withdrawn from trapout plate 45 pass through line 52 to the side stripper 53 which is designed to separate the low boiling hydrocarbons from the polymers boiling within the gasoline boiling range. The vapors are withdrawn from the top of the side stripper through conduit 54 and returned to the tower at a .range-a-re withdrawn from the bottom of the.

side stripper through line 55, cooler' 66 and then passed to storage. Thesehydrocarbons are made up mostly of dimers and trimers produced by the pelymerization reaction. They maybe used as such as motor fuels or blended with straight run or cracked gasolines in order to raise their antiknock value. v

The overhead from fractionating tower 34 consists mostly of low boiling hydrocarbons which are usually top light for use in motor fuels. These products pass through line 51 to the cooler 68 and thence to the separator reflux drum 59. The

uncondensed gases are removed from the top of the separator through line 60 and the products which liquefy are withdrawn from the bottom thereof through line BI- and valved conduit 62. A portion of the liquefied constituent in line 6| is passed through line 63 with the aid of pump 64 and returned to the top of the fractionating tower 34 for use as reflux.

The amount of boron fluoride employed to polymerizethe unsaturated hydrocarbons may vary over a wide range, but generally from about 0.002 to 0.l cubic foot of boron fluoride should be present in the coils 12 for each cu. ft. of gas, measured at 60 F., introduced therein. Since, the boron fluoride-hydrocarbon complex is broken down into boron fluoride and polymer, we are able to recycle this boron fluoride and thereby avoid the necessity of continuously adding boron fluoride catalyst to the system through line l8. Small amounts of boron fluoride may be added at intervals to compensate for losses. A time of. contact from one second or a few seconds or about one minute to 10 minutes may be used in coils l2.

Since boron fluoride is corrosive, we prefer to use 'a non-corrosive alloy lining in the equipment used in the process in order to minimize corrosion. If desired, the gases in line 44 and the liquid polymers in lines and 32 may be washed with an absorbing agent such as water, alkaline solutions, aqueous ammonia, etc. for thepurpose of removing boron fluoride.

It is apparent from the foregoing description of ourcatalytic polymerization process that an admixture of hydrocarbons containing unsaturated hydrocarbons, particularly the butylenes and propylene, can be polymerized into hydrocarbon motor fuels without resorting to very high temperatures andpressures. By operating the temperature regulator I 3 within the range of temperatures hereinbefore specified, we have found that a high yield of hydrocarbons of high antiknock rating boiling within the gasoline boiling range are produced by our process.

Referring to Figure 2, the feed gases enter the system through valved conduit 66 and 'are passed into the lower portion of tower 66. I Boron fluoride gas enters the tower 66 through line 61 at a point near but below the inlet line 65. Hot

oil, steam or any suitable heating or cooling medium is passed through the coils 68 by aid of conduits 69 and 10 in order to maintain the temperature of the reaction zone in the lower part of the tower within the range of 300 to about 500 F. Within this range of temperatures the boron fluoride polymerizes the unsaturated constituents in the charging stock into higher boilingv hydrocarbons without the formation of a stable boron fluoride-hydrocarbon complex. The pressure-in tower is maintained within the range of about p -500 lbs. per square inch'and under the temperature and pressure conditions maintained in tower 66, the polymers form in the reaction zone,

condense and pass to the bottom of the tower as indicated by the drawings. The unreacted gases and boron fluoride rise up through the tower into zones maintained at progressively,

lower temperatures. The top of tower 66 is maintained at a temperature below F. and preferably within the range of 50-100 F. The boron fluoride and unreacted gases which pass from the reaction zone to the upper part 01' the tower,

continue to react and form higher boiling. hydrocarbons but at temperatures below 200 F., a boron fluoride-hydrocarbon complex is formed and trap-out plates H and 12 are provided in tower 66, usually at points up above the middle section, for the purpose of collecting the boron fluoridehydrocarbon complex. As this-complex is collected by the trap-out plates it is withdrawn through lines 13 and 14 and passed by line 15 back to the lower part of the tower and is introduced, preferably below the feed point, into vided in lines 13 and 14 for the purpose of main:

taining a liquid level on the trap-out'plates II tower 66 in order to assist in the fractionation of the constituents therein and promote a more e cient polymerization reaction.

The unpolymerized hydrocarbons, such as proane and butane, which may be present in the feed gases, pass from the top of tower 66 through line 18 to the cooler 19 and thence to the reflux drum 80 where the condensed hydrocarbons are withdrawn from the bottom through valved conduit 8| by pump 82 and returned to the top of the tower through line 83 and used as reflux. An

inter-cooler or reflux coils may be provided in the top part of tower 66 in order to maintain the desired temperature in the upper zone of the tower. A part of the polymer withdrawn from the bottpm of tower 66 through line 84 is passed through valved conduit 85 to the cooler 86 then joined with the products in line 83 for use as reflux. The polymer or reflux will react with boron fluoride in the gases passing up the tower forming boron fluoride-hydrocarbon complex and will also assist in maintaining the desired temperature in the upper part of tower 66.

The gases removed overhead from reflux drum 80 are passed through line 81 to the lower part of a scrubber 88 where they are washed with an absorbing agent, previously described, to remove the traces of boron fluoride remaining in the gases.

The gases from the overhead of the washer 88 may be used as fuel gases or disposed of in any convenient way. A valved draw-oil and charge line 88a is provided in-the lower part of the washer '88. The liquid polymers withdrawn from the bottom of tower 66 throughvalved conduit 84 arepassed to the bottom of the scrubber 89 and there permitted to pass up through water orother absorbing agent where any traces of boand r and 12. Bubble trays or baflies may be placed in.

ron fluoride are removed. A valved draw-off and charge line 89a is providedat the bottom of the scrubber 89. q

The liquid polymers which rise to the top of the aqueous medium in washer 89 are withdrawn through conduit 90 and passed to the fractionating tower 9| through valved conduits 92 and 92a. Fractionating tower 9I is of conventional construction and is operated so as to cut the polymer into a fraction boiling within the gasoline range and a heavier fraction, Liquids in the lower part of fractionating tower 9I- are withdrawn from trap-out plate 93 through conduit 94 and passed to the reboiler 95 and then returned to the lower part of the tower through line 95. The heat supplied by the reboiler 95 permits the polymers in tower 9| to be fractionated as above indicated and baiile plates or trays 91 are employed in the fractionating tower 9|; The heavy polymers, usually those hydrocarbons boiling above about 420 F. are withdrawn from the bottom of fractionating tower 9| through valved conduit 98 and the lower boiling hydrocarbons are removed from the top of the fractionating tower through conduit 99. The fraction of hydrocar-' bons withdrawn from line 99 may be blended with straight run or cracked gasoline and used as a motor fuel. A portion of the heavy polymer from line 98 may be recycled to tower 66 through line 93 and other lines not shown for the same purposes ;as described in connection with the material from line 84.

Since the boron fluoride-hydrocarbon complex is broken down in the operation of tower 66 into boron fluoride and polymer, we are able to recycle the boron fluoride and thereby avoid the necessity of continuously adding boron fluoride catalyst to. the system through conduit 01. However, small v...'ar'n'ounts of boron fluoride may be added to compensate for losses. The amount of b'oronfluoride employed to polymerize the unsaturated hydrocarbons may vary over a wide range, but generally from about .002 to .100 cu. ft. of boron fluoride gas should be present in tower $6 for each cu. ft. of reaction space therein.

Referring to Figure 3, gases containing olefins, preferably an admixture of gases containing propylene and butylenes as the predominating constituents available in either the gaseous or liquid state, enter the system through line I00, are raised bywcompressor pump IN to the desired pressure and split between valved conduits I02 and I03. The feed gases in line I03 pass through the coils I 04 in the temperature regulator I05 where they are heated to a temperature within the range of 300-700 F. Any suitable heating means such as stream or hot oil is'circulated through the temperature regulator I05 with the aid of conduits I and I01. The catalyst, boron fluoride, enters the system through line I08 and is split into two streams by valved conduits I09 and H0. The boron fluoride gas in line IIO passes to the coils I04 at a point intermediate the two ends of the temperature regulator I 05. By introducing the feed gases.

catalyst into coils I04 at a point down stream, the first part of the coil I04 serves as a heater forthe The boron fluoride polymerizes the unsaturated hydrocarbons in the feed gases into higher boiling hydrocarbons and the reaction products from the coils I04 pass to the cooler III' which lowers the temperature of the reaction products to about 200 F. or lower.

The cooled products then pass from the cooler through line III to the separator II3 where the tree polymers. along with a. portion of the fluoride-hydrocarbon complex formed in the process separate as a liquid product. The boron fluoride and unpolymerized gases pass from the top of the separator I I3 through line I I4 and enter the second temperature regulator I I which is operated at a temperature below 200 F. and pref-. erably within the range of 200-90 F. The products in line II4 join a portion of the feed gases passed through line I02 and the admixture passes into the coils I I6 where the polymerization reaction is continued. At temperatures below 200 F. the boron fluoride forms the complex. Any suitable temperature controlling medium may be circulated around the coils H6 in the temperature regulator with the aid of conduits H1 and W8. If desired, an additional quantity of boron fluoride may be introduced into the coils I I6 through conduit I09, but this is not preferred. 1

The effluent from coils H6 is withdrawn through line I I9 and mixed with the liquid products withdrawn from the bottom of separator I I3 through valved conduit I20. The valve in conduit I20 controls the liquid level in separator H3. The admixture of the products from lines I I9 and I20 pass to the'liquid separator I2I and there permitted to separate into liquid polymers and the boron fluoride-hydrocarbon complex. Usually a liquid level, as indicated by line I22, is maintained in the lower part of the separator below the point where the products enter the separator. The boronfluoride-hydrocarbon complex is withdrawn from the bottom part of the separator through conduit I23 with the. aid of pump I24 and returned to an intermediate portion of the coils I04 in temperature regulator I05. At the high temperature maintained in the coils I04, this complea is decomposed. into liquid polymer and boron fluoride gas. The latter'reacts with the polymer- .izable constituents in the feed stock and repeats the cycle.

The liquid polymers and unreacted constituents in the upper part of separator I2I are withdrawn therefrom by line I25 and introduced into the lower part of the tower I26 where the products are permitted to rise through an absorbing agent that will absorb the trace of boron fluoride in the products withdrawn through line I25. Since boron fluoride is soluble in water, the products in tower I26 may be scrubbed with water in order to remove the entrained boron fluoride. A valved draw-off I21 is provided in the lower part of the washer I26. The line I28 indicates the liquid level maintained therein when a solution is used to neutralize or remove the boron fluoride from the products therein. The products are withdrawn from the top of tower I20 through line I29 to the heater I30 and then introduced into the fractionating tower I3I. The fractionati g tower is of the conventional type and may be perated in a manner well known to the art. Usually the products in line I29 are introduced into the tower at a point below the trap-out plate used for withdrawing the hydrocarbons' or polymers boiling within the gasoline range. a. A trap-out tray I32 is provided in the lower part of the tower I3I and the heavy products are withdrawn through line I33 and passed to the reboiler I34 and then returned to the bottom of the tower through line I35. The reboiler provides sufli'cient heat for the operation of the tower I3I. The heavy polymers, usually those polymers boiling above about 420 F., are withdrawn from the bottom of tower I3I through conduit I35, pass through the heat exchanger I30 and thence to storage through line I31. These polymers may be used as a charging stock for a cracking unit where they are cracked into hydrocarbons-boiling within the gasoline boiling range. The products in the middle portion of the tower are withdrawn from trap-outplate I88 by line I39 and passed to a side stripper similar to that shown in Figure 1. The bottoms from this side stripper constitute the fraction of polymers boiling within the gasoline range and the light products withdrawn from the top of the stripper are returned to the tower I3'I. The gaseous products in the fractionating tower are withdrawn through line I40 and passed to the cooler HI and thence to the refluxdrum I42. The uncondensed materials are withdrawn from the top of the refluxdrum through valved con-j duit I43. The condensate in the reflux drum is withdrawn through line I44. and passed to storage through valved conduit I45. A'portion or all of this condensate may be passed through line I46 with the aid of pump I41 and returned to the top of the fractionating tower I3I for use as re-' flux. The conventional type of bubble trays I48 are .used in tower I3I in order to assist in the fractionation of the constituents therein.

The amount of catalyst and pressure conditions employed in our process as shown by Figure .3, may be the same as those given in connection with Figure 1. By providing a second reaction coil in temperature regulator H5 and operating the same at a temperature below 200 R, we can recover the boron fluoride catalyst in the form of a boron fluoride-hydrocarbon complex. In addition to this feature, we are also able to polymerize those constituents which escape polymerization ,in reaction coils I04 By maintaining the temperature in reaction coils I04 above 300 F. and below 700 F.', we are able-to produce a very large amount of liquid polymers which boil within the gasoline boiling range.

Referring to Figure 4, the feed enters the system through line I50, is raised by pump or compressor I5I to the desired pressure,- passed I through the coils I52 m the heater I53 and then passed through conduit I54 to the lower part of the tower or reactor I55. Steam, hot oil or any suitable heating means may be circulated around the coils in heater I53 by conduits I56 and I 51 in order to heat the feed gases. The,

above about 200 F. and consequently this comboron fluoride catalyst enters the system through conduit I58, pump I59 and passed by conduit I60 to the lower part of tower I55 and there'permitted to mix with the feed gases; The temperature maintained in the lower part of tower I55 ranges from about 300 to 500 F. The remaining part of the tower is maintained at progressively lower temperatures and the 'top part of the tower is maintained at a temperature below about 150 F. and preferably within the range of 150-80" F.

. The unsaturated gases are polymerized by the boron fluoride in the lower part of tower I55 and the liquid polymers resulting from this reaction condense and pass to the bottom of the tower where they are withdrawn and treated as hereinafter indicated. The boron fluoride-hydrocarbon complex is not stable at temperatures plex does not exist to an appreciable extent in the reaction zone which makes up the lower space in tower I55. The unreacted gases and boron fluoride pass up the tower to zones which are maintained at temperatures below 200 F. and preferably below 150 F. In these cooler zones the boron fluoride forms the boron fluoride-- I hydrocarbon complex which condenses and is collected by the. trap-out plates III and I62. Draw-oil lines I68 and I64 communicate with the trap-out plates and pass the complex to conduit I65 which returns the same to the hot reaction zone in the lower part of the tower. Conduit I66 enters the tower at about but below the point where the feed gases and boron fluoride enter the tower. At the temperature maintained in.

the lower part of tower I55, theboron fluoride hydrocarbon complex is decomposed into free polymer and boron fluoride. The boron fluoride again passes up through the tower to further polymerize unsaturated hydrocarbons and form passed through valved conduit I68 to asection' of the tower up above the middle portion and there permitted to react with the boron fluoride. By increasing the concentration of oleflns inthe upper part of tower I 55, we can insure the formation of theboron fluoride-hydrocarbon complex with substantially all of the boron fluoride in the upper part of the tower. Varying amounts of feed gas may be diverted through line I68 and the ratio between the feed gas passing through the heater I53 and conduit I68 may vary over a wide range but, generally, the amount of feed gas introduced into the system through line I68 should be only sufllcient to insure that only a small amount of boron fluoride escapes through line An economic balance must be struck between olefln and boron fluoride 10;...

A trap-out plate I60 is provided near the bottom of tower I55 where a part of the polymer is withdrawn through line I10, heated in the reboiler III and returned to the lower part of the tower through line I72. The reboiler insures the maintenance of a temperature above 3001". in

inch and baille trays or bubble plates I'll may 1 A be provided in the tower in order to assist in con-- tacting the boron fluoride gas with the unreacted gases and to also assist in fractionating the liquid materials from the unreacted gases.

The overhead from tower I55 is passed by line I14 to the cooler I15 and thence to the reflux drum I16. The condensate in the lower part of drum I'I6is withdrawn through line I 11 by pump I18 and returned through line I18 to the top of tower I55 and used as reflux. An intercooler or reflux coils may also be provided in the top part of the tower I55. The overhead from reflux drum I16 is withdrawn through line I60 and passed to the bottom part of the washer III where it is permitted to pass up through a boron fluoride absorbing agent to remove traces of boron fluoride contained in the unreacted-gases. The scrubbed gases collect above the liquid level in washer I8I and are withdrawn through line.

I82. A valved draw-off line or charge line I68 is provided in the lower part. of the washer.

The liquid polymers in thebottom part 0! tower I 55 are withdrawn through line I84 by pump or valve I85 and thence to the bottom part of the scrubber I8'I containing an absorbing agent where the traces of boron fluoride are removed therefrom.. A valved conduit I88 is provided in.

the lower part of washer I61 so thatthe contents 7;

tially the same manner as the fractionating tower ll of Figure 2. Tower ISfl separates the liquid polymer into two fractions one of which boils above the gasoline boiling range and the other containing hydrocarbons which boil within and below the gasoline boiling range. A trapout plate I93 is provided in the lower part of the tower and the heavy polymers are withdrawn through line I, heated in the reboiler I95 and returned to the bottom part of the tower through line I. The heat supplied by the reboiler I9! is suflicient to fractionate the constituents in the tower and suitable fractionating means such as baIIIe plates and bubble plates I91 are provided in the tower in order to assist fractionation. Liquid heavy polymers are withdrawn from the bottom of fractionating tower I90 through valved conduit I".

The overhead from .fractionating tower I90 passes through line I99 to the cooler 200 and thence to the reflux 'drum 2!. Liquid condensate is withdrawn from the bottom of reflux drum 2III by conduit 202 and a part of this condensate is forced by pump 203 through conduit 2" to the top part of the fractionating tower I90 and used as reflux. The remainder of the condensate withdrawn through line 202, is passed to storage through valved conduit as polymerlzed gasoline. If desired, this gasoline may- "be further fractionated and blended with straight-run or cracked gasoline for use as 'motor fuel. The uncondensed gases in the top part of iaiux drum 2M are withdrawn through conduit The amount of boron fluoride employed to polymerize the unsaturated hydrocarbons may vary over a wide range but generally from about -.002 to 0.10 cu. ft. of boron fluoride should be present in tower I55 for each cubic foot of space contained th er in. Since the boron fluoridehydrocarbon c mplex is broken down into boron fluoride and polymer, we are able to recycle this boron fluoride and thereby avoid the necessity of continuouslyadding boron fluoride catalyst to the system through line I58. Small amounts of boron fluoride may be added at intervals to compensate for losses. I

Four methods of operation of a boron fluoride catalytic gas polymerization process have been described. In all cases temperatures distinctly above the boron fluoride-hydrocarbon complex decomposition temperature have been used for the main polymerization reaction. In all cases the formation of the boron-fluoride-hydrocarbon complex has been used to prevent the loss of boron fluoride from the system.

In' connection with Figures 1 and 2, hydrocarbon products from any one of three sources or combinations thereof have been used ,to contact the boron fluoride to form the boron fluoride-hydrocarbon complex. These three sources are: first, raw polymer; second, heavy gasolinefree polymer; and third, hydrocarbons from the arcane decomposition of the boron fluoride-hydrocarbon complex.

In connection with Figures 3 and 4, the use of a second polymerization step with further fresh feed at a temperature below the decomposition temperature of the boron fluoride-hydrocarbon complex has been used to form the -boron fluoride-hydrocarbon complex and avoid loss of boron fluoride.

- We further contemplate a combination of these two methods, polymer scrubbing and a second polymerization, to prevent the loss of boron fluoride.

While we have described our process with reference to four different types of operation and set forth certain temperature and pressure conditions, it should be understood that these .conditions may be varied somewhat without departing from the scope of our invention. Also, the

amount of boron fluoride gas used to polymerize the hydrocarbons may vary considerably but the It should be noted that the operations shown amounts herein specifled with respect to the four types of operation will give satisfactory results. If desired, a small amount of hydrofluoric acid may be added to the boron fluoride catalyst. Generally, a small and preferably controlled amount of moisture in the feed gases tends to assist the polymerization reaction.

We claim: 1

. 1. The method of converting gaseous hydrocarbons containingcomponents such as butylene and propylene into liquid products having a substantial fraction within the gasoline boiling range which method comprises introducing compressed gases containing oleflns to a high temperature contacting zone maintained at a temperature of about 300 to 500 F. and a pressure of about 100 to 500 lbs/sq. in., introducing a small amount of boron fluoride gas into said zone, removing. heavy polymerization products from the lower part of said zone, passing boron fluoride and gaseous products into a low temperature zone for further reaction, whereby boron fluoride hydro-" carbon complexes are formed, returning said boron fluoride complexes from said low temperature zone to the zone which is maintained at 300 to 500 F. for the recovery of boron fluoride therefrom, scrubbing the liquid products of the reaction to remove traces of boron fluoride and fractionating said liquid products to separate components of the gasoline boiling range from higher boiling and lower boiling components.

2. The method of claim 1 which includes the step of introducing polymerized materials from the lower part of the initial contacting zone to the low temperature zone for reaction with boron fluoride therein to form the boron fluoride complex.

3. The method of converting hydrocarbon gases containing oleflns such as butylene and propylene into liquids, a substantial portion of which are within the gasoline boiling range,

I the gasoline boiling range and the lighter and with boron fluoride at a temperature of from about 250 to 500F., cooling the contacted materials to a temperature below 200 F., separating polymerized products from boron fluoride and unreacted gases, contacting said boron fluoride and unreacted gases with i'urther amounts or olefinic gases at a temperature of from 50 to 200 F. whereby polymerization products and boron fluoride complexes are formed, separating polymerization products from boronfluoride complexes, and fractionating .the polymerization products to separate components boiling within heavier products respectively.

4. The method of claim 3 which includes the step of returning the separated boron fluoride complex to theinitial contacting zone.

5. The method of claim 3 which includes the steps of decomposing the separated complex, re-

covering gasoline from the hydrocarbon material separated from said complex and returning boron fluoride separated from said complex to the initial contacting step.

'6. The method of converting oleflnic gases into the second contacting step into a hydrocarbon boron fluoride complex, separating said complex from hydrocarbon material and decomposing said complex with heat into boron fluoride and additional hydrocarbon material, scrubbing and fractionating said hydrocarbon material to recover gasoline therefrom, and returning boron fluoride from said complex to the initial contacting step."

7. The process of converting an admixture of normally gaseous hydrocarbons containing olefins into'liquid hydrocarbons, the steps comprising contacting under pressure in a reaction zone an admixture of normally gaseous hydrocarbons containing oleflns with a boron halide catalyst at a temperature within; the range of 300-700 F. to convert a portion of the hydrocarbons into liquid hydrocarbons, passing the unreacted gases admixed with the boron halide catalyst into a second reaction zone maintained at a temperature below 200 F. to eflect the formation of a boron-halide-hydrocarbon complex, removing the boron-halide-hydrocarbon complex from the second reaction zone 'and heating it to a temperature above about 250 F. todecompose it into boron halide and liquid hydrocarbons, and recovering the liquid hydrocarbons produced in the process. Q r

8. The process of claim 7 wherein boron fluoride is used as the catalyst.

9. The process of converting an admixture of normally gaseous hydrocarbons containing butyienes into liquid hydrocarbons, the steps comprising contacting under'pressure in a'reaction zone an admixture of normally gaseous hydrocarbons containing butylenes with a boron halide catalyst at a temperature within therange of BOO-500 F. to convert a portion of the hydrocarbons into liquid hydrocarbons, passing the unreacted gases admixed with bordn halide" catalyst into a second reaction zone maintained at a temperature below 150 F. to effect the formation. of a boron-halide-hydroca'rbon complex, removing the boron-halide-hydrocarbon complex.

from the second reaction zone and heating it to a temperature above about 200? 1".to decompfse A 7 it into boron halide and liquid hydrocarbons and reusing the thus generated boron halide in. the first reaction zone to effect further conversion,

and recovering the liquid-hydrocarbons produced in the process.

10. The method of claim 9 wherein about 0.002

to 0.1 cubic foot of boron fluoride are introduced into the flrst mentioned reaction zone for each cubic foot of gaseous hydrocarbons,.the volumefl in both cases being based on gases at atmospheric;

- normally gaseous'hydrocarbons containing oleflns into liquid hydrocarbons, the steps comprising contacting under pressure in a reaction zone an admixture of normally gaseous hydrocarbons containing oleflns with a boron/ halide catalyst at a temperature within the range of 300-700" F. to convert a portion of the normally gaseous hydrocarbons into liquid hydrocarbons, passingthe unreacted gases admixed with the boron halide catalyst into a second reaction zone maintained at a temperature below about 200 F. to eflect the formation of a boron-halide-hydrocarbon complex, recycling a portion of theboron-halidehydrocarbon complex to the first reactiorrzone where it is decomposedvinto boron halide and liquid hydrocarbons, and recovering the liquid hydrocarbons produced in the process.

13. The process of converting an admixture of normally gaseous hydrocarbons containing butylenes into liquid hydrocarbons, the steps comprising contacting under pressure in a reaction zone an admixture of normally gaseous hydrocarbons containing butylenes with boron fluoride at a temperature within the range'oi 300-500". F. to convert a portion of the hydrocarbons into liquid hydrocarbons, passing the unreacted. hydrocarbons admixed with boron fluoride into a second reaction zone maintained at a temperature below 150 F; to eifect the formation of a boron-fluoride-hydrocarbon complex, recycling a portion of the boron-fluoride-hydrocarbon complex to the first reaction zone where it is decomposed into boron fluoride and liquid hydrocarbons and the thus liberated boron fluoride catalyzes the conversion of theadmixture of normally gaseous ydrocarbons containing butylene entering the system, recovering and fractionating the liquid hydrocarbons produced in the process.

14. The process of converting an admixture of normally gaseous hydrocarbons containing propylene andsbutylenes into liquid hydrocarbons,

the'steps comprising contacting under pr ssure in a reaction zone an admixture of normally gaseous hydrocarbons containing propylene and,

butylenes with boron fluoride at a temperature within the range of 3 700 F. to convert a portton of'the hydrocarbons into liquid hydrocarbons, passing the products from the first reaction zone into a second reaction zone maintained at a temperature below 200 F. 'to effect the formation of a boron-fluoride-hydrocarbon complex, passing the liquid products from the second reaction zone into a separating zone wherein liquid. hydrocarbons are separated from'the boron-fluoi ride-hydrocarbon complex, heating the boronfluoride-hydrocarbon complex to decompose it into boron fluoride and liquid hydrocarbons and recyclingthe thus liberated boron fluoride to the flrst reaction zone, and recovering the liquid hydrocarbons produced in the process.

15. The process of converting an admixture oi! normally gaseous hydrocarbons containing propylene and butylenes into liquid hydrocarbons,

the steps comprising introducing the admixture of gases and gaseous boron fluoride into the lower part of an upright elongated reaction zone wherein a part of the hydrocarbons are converted by the boron fluoride rinto liquid hydrocarbons, maintaining the temperature in the lower part of said reaction zone within the rangeof 300- 500 F. and maintaining the temperature in the top part of said reaction zone below 200 F., pass- 15 ing the unreacted gases and boron fluoride to the upper part of said reaction zone and also introducing into the upper part of said reaction zone an admixture of normally gaseous hydrocarbons -containing propylene and butylenes wherein the boron fluoride and unsaturated hydrocarbons react to form a boron-fluoride-hydrocarbon complex compound, returning the boron-fluoride-hy- 

